1. Field of the Invention
The invention relates to a casting stalk used primarily for low-pressure casters.
2. Description of the Related Art
Conventional casting stalks that are extensively used for low pressure castings are of the thermally insulating type. They include various heat retaining layers formed on both inner and outer surfaces of a metallic cylindrical body, known as the "core". These layers protect the cylindrical body from molten metal so that the molten metal can be maintained at the desired temperature for casting.
In the conventional casting stalk, as described above, air can easily enter into the metallic cylindrical body and cause a problem with casting. When the cylindrical body is formed from a s steel pipe, there is an additional problem. The steel pipe is subject to corrosion and erosion by a molten bath of an aluminum alloy. If the molten aluminum alloy enters through cracks present on the outer thermally insulating member to reach the steel pipe, the steel pipe is gradually corroded and eroded. This, in turn, allows air to enter into the stalk during pressurized casting. This can make casting impossible when there is sufficient air leakage.